By crux you mean the 1 paragraph at the end where it mentions performance? That's basically a footnote to an article that spends the other 99% describing javascript variable hoisting. They cite an 8% performance boost but they don't analyze it, instead just claiming it is a lot of work for the interpreter and linking to a github issue. They've run no benchmarks. They have shown no interpreter internals. They just report that one project saw an 8% performance improvement.

They did a great job of explaining javascript variable hoisting, but that's all that they have explained.